Control the wall drying

It is easier to get the previously applied cob and the new cob to stick together
if the moisture levels are similar. This means that you are riding the fine
line between keeping the top of the wall as moist as possible so the next
cob layer will adhere to it, and letting the lower part of the wall dry enough
to support the weight of more cob.

Cover the tops of the walls with dampened straw, burlap sacks, and/or tarps
and kiss it good night.

If you suspect heavy rain is coming, you can cover the walls with tarps or
sacks. To speed up drying, you can place lots of dry straw on top of the wall
under the tarps or sacks. If it's likely to be windy, weigh down the covers
so they won't blow off. The rain won't hurt your wall seriously but it will,
obviously, slow down the drying time.

It's a good idea to keep your fresh walls out of strong direct sun and harsh
winds, which will dry the outside surface too quickly, and can cause cracks
on the dried surface as the inner cob dries and shrinks. Protect the walls with
shade or by covering them. If you're cobbing where the temperature drops below
freezing at night, pile straw bales or loose straw on the sides and on top of
the walls to prevent them from cracking up. You could use old sleeping bags
or anything that insulates. Take the covers off during the day so the walls
can dry.

If you'll be back to do some more cobbing in the next few days, stop working
on the walls while you still have enough energy to make up some cob mixes to
cure. It's a delight to have mixes ready at the start of a new cobbing day.
Because these mixes will be curing and drying out for awhile, you can mix them
extra wet which is easier and quicker.

I also like to tidy up so when I return to the site it feels welcoming, and
I can find my clean tools.

It's as simple as that! Keep cobbing and sculpt your home!

What if the cob dries out completely before you get back to it?

It's OK. Fill the holes in the top of the wall again and again with water
until the cob is rehydrated. Be careful to really incorporate the first new
layer of cob. Use a stick and push the new cob hard into the old. Another trick
is to sew the layers together with straw, pushing pieces of straw through the
new mix into the holes in the old cob.

If you know that you'll be leaving the partially finished building for
a long time, there are a few things you can do to make it easier to connect
the next 'layer' of cob.

Leave the top of the walls rough, with lots of humps and holes and valleys.

Make the re-wetting holes extra wide and deep.

Cover the top of the walls with wet burlap sacks and let the rain fall
onto the walls.

You can push small sticks or bamboo into the cob on the tops of the walls
4 or 5 inches down, leaving 4 or 5 inches sticking up. Put them every foot
or so and poking out at different angles. The sticks will be buried in the
new cob when you continue building.

Patching an already dried wall

Plaster adheres beautifully to cob and will cover minor dips and smooth out
the overall contours of the walls. But if you want to make a more major change
and add new cob to the old, start by wetting the dry cob as much as possible.
Drill, carve, or hack with a hammer claw holes in the hardened cob for the new
cob to hold onto. You can hammer some old nails partway into the dry cob to
help support the cob you're adding.

How to destroy dry cob

If you want to add a window or door, or change something in an already dry
wall, get out the battering ram. You will soon have a new respect for the strength
of cob and a healthy appreciation for taking the time to plan carefully. A 3/4
inch steel pipe can be sledge hammered through the wall many times where you
want an opening. Wetting the wall again and again helps. Try an axe or hatchet
to chop out what's left. It is much easier to fill in an unwanted door or window
than to chop one out!

Push straw into the tops of the wall leaving some of the straw sticking out
to help knit the next cob application to the previous one.